Problem: Simplify the following expression: $a = \dfrac{1}{6p} - \dfrac{5}{8p}$
Explanation: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $6p$ and $8p$ $\lcm(6p, 8p) = 24p$ $ a = \dfrac{4}{4} \cdot \dfrac{1}{6p} - \dfrac{3}{3} \cdot \dfrac{5}{8p} $ $a = \dfrac{4}{24p} - \dfrac{15}{24p}$ $a = \dfrac{4 -15}{24p}$ $a = \dfrac{-11}{24p}$